She's not that bad, actually ADC

I've ran into extremely few people who understand how to build classic MF. They either come in with a modern AD MF mentality and build around R (her worst ability by far) or build full AP E spam. I certainly don't think she's secretly one of the best ADCs in the game, but I disagree greatly with the sentiment that she's one of the worst characters in classic. Her w has been buffed to ramp even harder at early levels, and yet people still max q. I'll just state it outright: Classic MF is characterized by her W and is a hybrid on-hit marksman similar to Kayle and Kog'Maw. Ramping flat on hit magic damage makes you gradually turn extended fights, especially early and mid game. Most players underestimate MF's 1v1 potential and her DPS when fully ramped, so you catch a lot of people off guard just damage checking them.

Runepage has hybrid stats and a lot of flat magic pen. 9 flat pen + Malady's max 28 shred on-hit leaves most ADC's with negative MR (roster averages around 30, and if you get a Fiddle support/jungle that's another flat -10 just for him being in lane. Soraka also reduces flat MR with her q every cast, but most people solo lane with her in classic.

Surge is a very slept on summoner spell as well. Spiking your AP and AS so high for important fights is massive, and you make full use out of both stats. Always always always take Summoner's wrath if you go Surge. Skip first point in E until necessary. Going two points w at level 3 can win you fights that like 20-60 damage and a 20% slow for 80 mana cannot.

Waveclear with autos and W casts, not with Q or E or you'll run out of mana quick. Only use q while trading to either stack W as fast as possible or to get in an extra max stack w hit after fully stacking or to pick up a minion you would've lost otherwise. Thankfully, since you're maxing w, q only costs 70 mana early. Do not place faith in your ultimate. It will never do what you want it to do. R is a waveclear button, even built full AD the damage is negligible. Completely reasonable to skip points in R at level 11/16 for earlier spikes on your abilities that actually do things when you press the button.

YOU ARE NOT A CASTER! I cannot express this enough. Picking up items like Lich and Liandry's can give you decent poke if your team needs it, but your strength is in magic damage from on hits. Trying to play around q bounces, r angles, and e spam like modern MF WILL get you killed. You kite and you auto.